Inflammasomes are key for the release of the inflammatory cytokines IL-1?, IL-18 and the induction of pyroptotic cell death. In addition, inflammasomes release polymerized ASC danger particles (pASC), which perpetuate and propagate inflammasome responses to bystander cells and pASC as well as pASC auto- antibodies are found in inflammatory disease patient sera. In addition, cytokine release by the non-canonical inflammasome also requires the canonical NLRP3 inflammasome. However, the mechanisms by which inflammasomes are controlled are largely elusive. Excessive and uncontrolled NLRP3 and Pyrin inflammasome activity causes the autoinflammatory diseases Cryopyrinopathies and familial Mediterranean fever, respectively. Given the important roles of IL-1? and IL-18 in host defense and the pathology of inflammatory diseases, elucidating the mechanism of inflammasome activation is expected to have a major impact on the medical field and will be crucial for designing novel and improved treatment options for inflammatory disease patients. Using a proteomics approach, we discovered a novel inflammasome component and identified its role in mediating a novel and essential step of inflammasome activation, by promoting a distinct ubiquitination of inflammasome components, reminiscent to other key innate immune pathways. Furthermore, we discovered that this protein is part of the pASC danger particle released upon inflammasome activation. The research outlined in this proposal is geared to define the underlying molecular mechanism(s) of this novel activation step in human macrophages and our novel generated conditional knock-out mice, which are defect in inflammasome activation and the impact on inflammasome response propagation through pASC danger particles. We will perform a comprehensive analysis combining biochemical and genetic approaches focusing on key inflammasomes involved in human disease, namely NLRP3 and Pyrin and the diseases caused by their uncontrolled inflammasomes, as well as dissecting this activation and propagation mechanism in human Crypyrinopathy patients. We expect that our research will uncover novel molecular mechanisms that change our current understanding of the pathologies of inflammatory disease and the control mechanisms present in healthy individuals to prevent inappropriate inflammasome activation. Our studies will therefore be highly significant and relevant for better understanding disease pathologies and for providing the basis for developing novel therapies to benefit patients and will therefore positively affect human health.